The broad use of portable host computers, including laptops, notebooks, palmtops, Personal Digital Assistants (PDAs), and hand-held computers (hand-helds), has been severely hampered by limited capabilities for expansion or customization. Expansion and application customization has been performed via only one, or at most two, slots for removable expansion modules for I/O, I/O adapters, memories, and memory adapters. Memory expansion cards have included DRAM, SRAM, ROM, and Flash technologies. I/O expansion modules have included dedicated peripherals, networking, modems, wireless communications, serial I/O, and bar-code and other scanners.
Having only one slot meant choosing between memory or peripheral expansion. In two-slot implementations, one of the slots is generally used for peripheral expansion, and the other for memory expansion. As market forces and consumer demand are pushing future PDAs to be ever smaller, allocating packaging volume for two-slots will be increasingly viewed as a costly and nonviable solution.
If not further qualified, a general reference in this specification and the attached claims to the terms “expansion module” or “expansion card,” and possibly prefaced by “removable,” should be construed as a general reference to a class of generally enclosed compact expansion devices that provide fast, reliable, and robust repeated field insertion, removal, handling, and storage, ideally suited for closed-case, user-serviceable, plug-in expansion of portable and hand-held computing devices. If not further qualified, a general reference in this specification and the attached claims to the term “slot,” should be construed as a reference to the physical and electrical means by which a portable computing device receives a removable expansion module of the class just defined. A reference in this specification and the attached claims to the terms “closed-case,” or “sealed-case,” serves to indicate that insertion and removal of an expansion device does not involve significant reconfiguration or removal of the external casing of the computing device. Closed-case is not meant to foreclose the possible user removal of a protective access panel or the user opening of a hinged access door. Nor is it meant to foreclose that the casing may need to be removed for more significant events best performed by a qualified service person.
Memory and Expansion Module Standards
Two of the most popular industry standards for the slots and removable cards are the PC Card and the CompactFlash Card. The PC Card has a 16-bit variant, previously known as a PCMCIA card, and a newer 32-bit variant, also known as a Card-Bus card. PC Cards include Type I, Type II, and Type III devices. If not further qualified, a general reference to PC Cards in this specification and the attached claims should be construed to refer to any of the Card-Bus (32-bit), PCMCIA (16-bit), Type I, Type II, or Type III PC Card variants.
U.S. Pat. No. 5,815,426 ('426), ADAPTER FOR INTERFACING AN INSERTABLE/REMOVABLE DIGITAL MEMORY APPARATUS TO A HOST DATA PART, assigned to Nexcom Technology, and hereby incorporated by reference, describes these and other removable expansion card and memory types suitable for PDAs. In addition to the PC Card and CompactFlash Card formats, the '426 patent includes discussions of and references to Miniature Cards, Sold State Floppy Disk Cards (SSFDCs), MultiMediaCards (MMC), Integrated Circuit (IC) Cards (also known as Smart Cards), and Subscriber Identification Module (SIM) Cards.
CompactFlash Standards
FIGS. 1, 2, and 3 are different views of a prior art Type II CompactFlash Card. The physical, electrical, and software interface architecture of CompactFlash Cards (CF+ Cards and CF Cards) is taught in the CompactFlash Specification Revision 1.3, Copyright 1998, and the CF+ and CompactFlash Specification Revision 1.4, Copyright 1999, both by the CompactFlash Association (CFA), P.O. Box 51537, Palo Alto, Calif. 94303, and both of which are hereby incorporated by reference. FIGS. 1, 2, 3, part of 10, and part of 11 are reproduced or derived from the CompactFlash Specification Revision 1.3 document. Strictly speaking, CompactFlash nomenclature uses CF to denote cards that are primarily limited to flash data storage, and uses CF+ to denote cards that may have any or all of: flash data storage, I/O devices, and magnetic disk data storage. CF and CF+ cards presently include Type I (3.3 mm thick) and Type II (5 mm thick) devices. Both Type I and Type II CF cards are 36.4 mm long by 42.8 mm wide, or roughly “matchbook-sized.” A Type III device is being defined as discussed in a later section herein. If not further qualified, a general reference to CompactFlash (or CF) in this specification and the attached claims should be construed to refer to any of the CF, CF+, Type I, Type II, or Type III CompactFlash variants.
U.S. Pat. No. 5,887,145 ('145), REMOVABLE MOTHER/DAUGHTER PERIPHERAL CARD, assigned to SanDisk Corporation, and hereby incorporated by reference, describes the required features of host systems for CompactFlash Cards, including controllers required by CompactFlash memory cards (CF cards) and comprehensive controllers required by CompactFlash memory and I/O cards (CF+ cards).
MultiMediaCard
FIGS. 4 and 5 represent a prior art MultiMediaCard form factor and its pad definitions. FIGS. 6 and 7 represent the prior art internal architecture of a generic MultiMediaCard and its registers. FIG. 8 illustrates the prior art functional partitioning of a generic MultiMediaCard system. FIG. 9 illustrates the prior art physical partitioning of a generic MultiMediaCard system.
The MMC and MMC related system issues are taught in the MultimediaCard System Summary Version 2.0, Copyright January 1999, by the MultiMediaCard Association, 19672 Stevens Creek Blvd., #404, Cupertino, Calif. 95014-2465, which is hereby incorporated by reference. FIGS. 4, 5, 6, 7, 8, 9, and part of 10 are reproduced or derived from the MultimediaCard System Summary document.
FIGS. 10 and 11 are different views comparing the form factors of the prior art CompactFlash Card (top) and MultiMediaCard (bottom). In each of 10 and 11, the CompactFlash Card and the MultiMediaCard are both roughly to equal scale.
Adapters for Removable Memories
Adapters exist or have been prophetically disclosed for physically and electrically coupling a removable memory on a slide, or stick, to a portable host via a removable expansion card of either the PCMCIA Card or CompactFlash Card form factors. The previously mentioned '426 patent describes such removable memory adapters. The focus of these existing memory adapters has been limited to merely providing an interface adapter, or bridge, between a first interface type (the host to removable-expansion-card interface) and a second interface type (the removable memory stick).
PC Card Mother and CompactFlash Card Daughter Combinations
Adapters exist or have been prophetically disclosed that comprise a special mother PC Card designed to accept one or more daughter CompactFlash Cards of one or more types. The previously '145 patent describes such CompactFlash adapters. The focus of these existing mother/daughter combinations has also been limited. First, the daughters have been used for memory expansion for the host platform, primarily in the form of flash-memory-based mass-storage-like devices. In this first approach, the mother card provides the requisite mass-storage controller functionality. Second, the daughters have been used for dedicated peripheral, I/O, or communication functions. In this second approach, the mother card has a so-called comprehensive controller that augments the mass-storage controller functionality with functions commonly required or useful to multiple daughter cards. Third, in a variation of either of the first two paradigms, functions of the general-purpose host may be relocated to the mother card.
Open-Back Module Expansion Standards
The previously discussed expansion module (or card) implementations have been of a first type wherein the module is mated with a closed-back mother device by (full or partial) insertion into a receiving chamber that is inside the external casing of the mother device. The chamber usually is of a standardized minimum width and insertion depth. The module insertion into the chamber is facilitated by edge-guides internal to the chamber and insertion is (usually) via a standardized minimum width×minimum height circumscribed portal (mouth, or orifice) in the mother device's external casing. The chamber portal is sometimes protected by a hinged or removable access panel or by a stub (a dummy card with an external end flanged to block off most of the portal) inserted into the chamber. According to this first type, the modules are designed to have dimensions compatible with the insertion depth×width, edge guides, and width×height orifice of the chamber.
For hand-held computer or PDA applications, a second type of expansion card also exists. The second type of expansion card makes use of an “open-back” (or open-face) industrial design approach previously applied to other hand-held devices, such as cellular telephones. In open-back hand-held devices, a standardized back-mount is made integral to the device. Families of removable components (such as batteries), varying widely in size and make-up but otherwise interchangeable, are designed to be compatible to the standardized back-mount. For open-back devices, the industrial design form-factor (appearance and volume) becomes a function of both the device and the mated component.
As applied to a hand-held mother device, an open-face expansion module is mated with a companion open-back device by (full or partial) insertion into a receiving recess of (usually) standardized width×minimum depth that is integral to, but substantially on the outside of, the device. The module insertion into the recess is via (usually) standardized module-edge guides incorporated into the open recess of the device. In a manner not unlike that for cards in closed-back expansion applications, open-face modules are designed to have dimensions compatible with the width×minimum depth and edge guides of the device recess. But since the recess of an open-back device by definition has no circumscribed portal, the module height and shape are largely unrestricted. Instead the height and shape of the interchangeable modules are restricted only by bounds imposed by practical utility, bounds imposed to avoid mechanical interference with other objects in common system configurations, and bounds imposed by ergonometric concerns.
Expansion modules for the Handspring Visor hand-held computer are an example of open-face expansion modules. These modules are designed in accordance with the Handspring Springboard expansion slot. The technology of the Springboard slot is publicly disclosed in a number of documents published on the Handspring Web-Site (http:\\www.handspring.com). “The Springboard Platform,” is a Handspring “white-paper” that broadly summarizes the technology. “Development Kit for Handspring Hand-held Computers,” Release 1.0, Document No. 80-0004-00, printed in 1999, gives a detailed description targeted at developers of Springboard modules. Open-face functionality is also proposed for next generation CompactFlash Type III (CF+ Type III) devices, whose specification is presently being defined by a working group within the Compact Flash Association. More specifically, the CF+ Type III devices are expected to enable hand-helds to continue to use the present 50-pin CompactFlash bus and connector, but make use of an open-back industrial design philosophy.
Background for Expansion Module Based I/O Functions
Techniques are known in the art for making and using systems that perform I/O functions in an expansion module. For example, see U.S. Pat. No. 5,671,374 ('374), PCMCIA INTERFACE CARD COUPLING INPUT DEVICES SUCH AS BARCODE SCANNING ENGINES TO PERSONAL DIGITAL ASSISTANTS AND PALMTOP COMPUTERS, assigned to TPS Electronics, which is hereby incorporated by reference. The '374 patent teaches the use of PDAs and similar hosts equipped with PC card interfaces for I/O devices including portable laser-scanners, magnetic stripe and ink readers, keyboards and keypads, OCR devices, and trackballs.
Techniques are also known in the art for making and using PC Card-based radios for applications based in a portable host. For example, see U.S. Pat. No. 5,519,577 ('577), SPREAD SPECTRUM RADIO INCORPORATED IN A PCMCIA TYPE II CARD HOLDER, assigned to Symbol Technologies, and hereby incorporated by reference.
Techniques are also known in the art for making and using disk emulation devices based on flash memory. For example, see U.S. Pat. No. 5,291,584 ('584), METHODS AND APPARATUS FOR HARD DISK EMULATION, assigned to Nexcom Technology, and hereby incorporated by reference.
Background for Relevant Application Specific Functions
Techniques are known in the art for making and using systems that download or capture compressed digital audio for storage and later playback using dedicated removable media. For example, U.S. Pat. No. 5,676,734 ('734), SYSTEM FOR TRANSMITTING DESIRED DIGITAL VIDEO OR AUDIO SIGNALS, assigned to Parsec Sight/Sound, and hereby incorporated by reference, teaches a system for transmitting digital video or audio signals over a telecommunications link from a first to a second party. In addition, U.S. Pat. No. 5,579,430 ('430), DIGITAL ENCODING PROCESS, assigned to Fraunhofer Gesellschaft zur Foerderung der angewandten Forschung e.V., and hereby incorporated by reference, teaches processes for encoding digitized analog signals. Such processes are useful for insuring high-quality reproduction while reducing transmission bandwidth and data storage requirements.
Techniques are also known in the art for making and using record and playback portable host devices based on a dedicated flash memory. For example, see U.S. Pat. No. 5,491,774 ('774), HAND-HELD RECORD AND PLAYBACK DEVICE WITH FLASH MEMORY, assigned to Comp General Corporation, and hereby incorporated by reference, and U.S. Pat. No. 5,839,108 ('108), FLASH MEMORY FILE SYSTEM IN A HAND-HELD RECORD AND PLAYBACK DEVICE, assigned to Norris Communications, also hereby incorporated by reference.
Limitations of Previous Approaches
In general purpose portable hosts, populating a finite-volume expansion slot has meant choosing one of either removable memory or peripheral expansion for that slot. When used for memory expansion, the removable memory has been limited to use for the system or application software running on the host. In essence, the removable memory has only been used as host-dedicated memory. This was done either directly, e.g., as some portion of the main-memory of the host, or indirectly as an emulation substitute for host mass-storage (i.e., disk drives). When used for I/O expansion, the expansion I/O-cards have not had access to a private removable media/memory. This has prevented portable computer hosts, such as PDAs, from being used as a customizable platform for many application-specific functions that require a removable memory dedicated to the application.
In general purpose portable hosts, populating a open-volume expansion slot has meant choosing one of either removable memory or peripheral expansion for that slot.